The development of models to predict the lifetime of polymer matrix composites, creep and fatigue, has been a great challenge over the past years. In this work an energy failure criterion is applied and assessed using published experimental data. Reiner and Weissenberg developed an energy failure criterion based on deviatoric free energy, In this theoretical model failure is part of the complete constitutive description of the material. The free energy is defined and related to the viscoelastic mechanical model. The failure criterion is defined and tested for some polymers. The experimental data for some materials at room temperature reveals some discrepancies and criterion modification is proposed. This modification is in accordance with results presented recently where the critical fracture energy was not constant but strain rate dependent. These energy based criteria are show to verify the universal relation between the creep rate and the time to failure expressed by the classical Monkman Grant relationship.
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